Fast drying emulsion systems

ABSTRACT

The drying time for aqueous asphalt emulsions used in the roofing and other waterproofing industries is shortened by separately applying an emulsion breaking agent to the substrate to be waterproofed, to the aqueous asphalt emulsion after it is applied, or both.

BACKGROUND AND SUMMARY

Asphalt emulsions are widely used in roofing and other waterproofingapplications. Unfortunately, most asphalt emulsions dry slowly, somerequiring as long as a few weeks to dry before other coatings can beapplied. This is inconvenient to both roofing contractor and buildingowner, since roofing projects cannot be finished quickly. Slow dryingtimes also limit the times when such emulsions can be applied, sincefreshly-applied asphalt emulsion layers can be damaged or ruined byunexpected rain.

It is already known to speed drying times of asphalt emulsions byco-spraying an emulsion-breaking agent, such as calcium chloride, withthe asphalt emulsion using a two component sprayer. See, for example,Usmani, Asphalt Science and Technology,© 1997, Marcel Dekker, Inc., pp297-306. This causes the emulsion to be broken, which in turn liberatesits aqueous phase for rapid evaporation. This approach, which is oftenseen in the mining industry, is not commonly used in the roofingindustry where the most popular spray equipment is capable of handlingonly a single component. Two-component sprayers are expensive anddifficult to operate and hence beyond the purview of most roofingcontractors.

It is also known to mix the emulsion-breaker with the asphalt emulsionbefore it is applied. See, p. 301 of the Usmani publication. Thisimpacts the emulsion's working time and therefore is undesirable incommercial operations.

In accordance with this disclosure, this slow-drying problem is obviatedby applying an emulsion-breaking agent to the surface to be waterproofedbefore the asphalt emulsion is applied, or by applying anemulsion-breaking agent to the asphalt emulsion after the emulsion isapplied to the surface to be waterproofed, or both. By following thisapproach, the freshly-applied asphalt emulsion is broken and its aqueousphase liberated for evaporation as soon as the emulsion is applied, orpromptly thereafter. However, because the emulsion breaker is appliedseparately from the emulsion, a two component sprayer is unnecessary.Therefore, this method can be easily practiced by the vast majority ofroofing contractors using conventional spray equipment.

Thus, this disclosure provides a process for applying a waterproofingasphalt layer to a substrate comprising applying an asphalt emulsion tothe substrate and contacting the asphalt emulsion with an emulsionbreaker to liberate the aqueous phase of the emulsion and thereby speedemulsion drying, the emulsion breaker being applied to the substratebefore the emulsion is applied to the substrate, or to the emulsionafter the emulsion is applied to the substrate, or both.

In addition, this disclosure also provides a new building product foruse in forming a waterproofing asphalt layer, the new building productcomprising a fibrous or foraminous web or layer of material impregnatedwith an emulsion breaker.

DETAILED DESCRIPTION

The Substrate

This disclosure is directed to applying waterproofing asphalt layers tosubstrates of any type or structure, in particular to any structurewhere asphalt protective layers have already been used in the past ormay be used in the future. For example, the technology described herecan be used for waterproofing concrete and/or cinderblock buildingfoundations, both above ground and underground, both inside and outside,and both new and used construction, for example. In addition, it canalso be used for waterproofing a wide variety of other objects, e.g.structural members and/or sheets or webs, both self-supporting andflexible, made from a wide variety of different materials includingsteel, aluminum and other metals, plastics, wood products and the like.Most commonly, however, the technology described here will be used forforming waterproof asphalt roofing systems.

Roofing systems can be formed in many different ways from a variety ofdifferent materials. A typical asphalt roofing system generally includesa foundation layer, such as a plywood or particle board base, forproviding structural integrity. Most roofing systems also include aninsulating layer on the foundation layer, which may be made from anymaterial providing a desired level of insulation. Examples includepolymer foams, especially those made from polyurethanes, polystyrene,polyisocyanate, polyester and the like, wood fiber, other cellulosicmaterials, and so forth. Many asphalt roofing systems also include oneor more additional “base sheets” on top of the insulation layer (orfoundation where the insulation layer is omitted), these base sheetstaking the form of a felt, fiberglass or polymer fiber mat or layerwhich has been previously impregnated with asphalt, normally molten,such that the base sheet, as a whole, is continuous and hencewaterproof.

Additionally or alternatively, such a base or reinforcing sheet can beimpregnated with asphalt by embedding such mat or layer in apreviously-applied layer of asphalt emulsion and then allowing theemulsion to dry. Multiple such base or reinforcing layers can also beused.

A layer of asphalt is then applied to this base or reinforcing sheet, orto the “final” or “outermost” base or reinforcing sheet when more thanone is used. For this purpose, the asphalt can be applied in molten,solution or emulsion form. Molten asphalt is difficult and unpleasant towork with, while the organic solvents needed to dissolve asphalt canhave undesirable odors. Therefore, aqueous asphalt emulsions represent apreferred method of application in most instances. In any event, theasphalt is applied in such a way that a continuous, coherent,solidified, waterproofing asphalt layer is formed. If desired, a layerof aggregate such as gravel or crushed stone can be applied to thiswaterproofing asphalt layer to enhance its abrasion resistance.

As indicated above, this disclosure is directed to forming waterproofingasphalt layers on substrates or any shape or structure and made from anymaterial. It will therefore be appreciated that by “substrate” is meantthe article to which an aqueous asphalt emulsion is applied so at toform a waterproof asphalt coating or protective layer once the aqueousphase of the emulsion has evaporated, regardless of the shape orcomposition of this article. Moreover, where more than one waterproofingprotective asphalt layer is applied using the technology of thisdisclosure, “substrate” refers to the article to which the first ofthese waterproofing protective asphalt layer is applied.

Aqueous Asphalt Emulsions

Aqueous asphalt emulsions are well known materials of commerce that havebeen used for many years in providing waterproofing protective layers.They are most commonly used in the paving industry in connections withproviding roads, streets, highways, etc. In addition, they are alsocommonly used in the building industries for providing asphalt roofingsystems as well as for waterproofing foundations, especially those madefrom poured concrete and cinderblock. When used in paving applications,they normally contain aggregate materials such as crushed stone, gravel,etc. When used in building applications, they normally contain little ifany aggregate or other filler.

The compositions and properties of aqueous asphalt emulsions are wellknown. In general, they are composed of three ingredients, asphalt,water and an emulsifier. Asphalt, which is sometimes known as “asphaltcement,” is a colloid composed of several fractions, the major onesbeing asphaltenes and maltenes. [Seehttp://www.blacklidgeemulsions.com/spec-3.htm] The asphaltenes, whichare the dispersed phase, are thought to furnish hardness while themaltenes, which are the continuous phase, are believed to provide theadhesive and ductile properties of the material and to influence itsviscosity and flow properties.

Most aqueous asphalt emulsions are made with asphalts in the 50-250penetration range, although climatic conditions may dictate that aharder or softer asphalt be used. Moreover, most aqueous asphaltemulsions contain about 40-70 wt. % asphalts, although greater or lesseramounts can be used if desired. For roofing and other buildingapplications, emulsions containing about 40-60 wt. % asphalts in the50-125 penetration range are more typical, while emulsions containingabout 55-70 wt. % asphalts in the 100-250 penetration range are moretypical for paving applications.

The second largest ingredient of asphalt emulsions is water. Since thepositive and negative ions found in naturally occurring water can affectemulsion stability, water containing impurities should be avoided whenmaking these products.

The third ingredient found in aqueous asphalt emulsions is theemulsifier or surface-active agent, commonly called a surfactant. Theemulsifier keeps the asphalt droplets in stable suspension and controlsthe breaking time. The surfactant changes the surface tension at theinterface, i.e., the area of contact between the asphalt droplets andthe water.

Two different types of emulsifier are normally used, anionic surfactantsand cationic surfactants. The most common anionic emulsifiers are fattyacids, which are wood-product derivates such as tall oil, rosin, andlignins. Anionic emulsifiers are saponified (turned into soap) byreacting with sodium hydroxide or potassium hydroxide. Most cationicemulsifiers are fatty amines (diamines, imidazolines, amidoamines, forexample). The amines are converted into soap by reacting with acid,usually hydrochloric. Another type of emulsifying agent, fattyquarternary ammonium salts, is used to produce cationic emulsions. Theyare water-soluble salts as produced and do not require the addition ofacid to make them water-soluble. They are stable, effective cationic(positively charged) emulsifiers.

Fillers and Other Optional Ingredients

In addition to the three basic components discussed above, aqueousasphalt emulsions can also include a variety of different fillers andother optional ingredients.

The most common example is the aggregates found in paving applications,such as crushed stone, gravel and so forth. Additional examples includeaccelerators, polymers, latexes and rubber modifiers. Particularexamples of elastomeric polymers commonly included in aqueous asphaltemulsions include copolymers of styrene and butadiene, styrene butadienerubber latexes, polychloroprene latex, polyisoprene, and crumb rubbermodifier. Particular examples of elastomeric polymers commonly includedin aqueous asphalt emulsions include ethylene vinyl acetate,polyethylene, polychloroprene latex and various compounds based onpolypropylene.

All of these fillers and optional ingredients can be included in theaqueous asphalt emulsions used in the technology of this disclosure fortheir known properties and effects.

Emulsion Breaker-Identity

In accordance with this disclosure, the aqueous asphalt emulsion iscontacted with an emulsion breaker to break the emulsion, therebyliberating or releasing the emulsion's water content for easy and rapidevaporation. In this context, an “emulsion breaker” or“emulsion-breaking agent” is any chemical which will render the asphaltemulsion unstable in the sense that a quantity of the emulsion in abeaker will separate into distinct aqueous and organic phases within onehour of being contacted with a sufficient amount of the chemical.

Chemicals which function as emulsion breakers are well known. See theUsmani publication cited above, for example. As appreciated by emulsionchemists, emulsion breakers are specific to the emulsifier used in thesystem. That is to say, the particular chemicals that will break aparticular aqueous asphalt emulsion depend primarily on the particularemulsifier from which the emulsion is made, since breaking an emulsionessentially amounts to counteracting the stabilizing effect provided bythat emulsifier. Therefore, the particular chemical selected forbreaking a particular emulsion must be capable of counteracting thestabilizing activity of the particular emulsifier employed.

Examples of chemicals which will break aqueous asphalt emulsions formedwith anionic surfactants include calcium chloride, calcium nitrate,aluminum chloride and ferric chloride. Examples of chemicals which willbreak aqueous asphalt emulsions formed with cationic surfactants includeany alkaline or acidic material which will change or shock the pH of thelatex to an unstable value.

Emulsion Breaker-Application

The emulsion breaker can be contacted with the aqueous asphalt emulsionin accordance with this disclosure by any means which does not involvesimultaneous application of both the emulsion breaker and the aqueousasphalt emulsion to the substrate. Normally, this will be done either byapplying the emulsion breaker to the substrate before the aqueousasphalt emulsion is applied, or by applying the emulsion breakerdirectly to the aqueous asphalt emulsion after the emulsion is appliedto the substrate and before it is dried. Both techniques can also beused together.

Thus for example, the emulsion breaker dissolved or dispersed in asuitable solvent such as water or other organic liquid can be sprayed onthe substrate before the aqueous asphalt emulsion is applied.Alternatively, the aqueous asphalt emulsion can be applied to thesubstrate first and the emulsion breaker dissolved or dispersed in asuitable solvent then applied to the previously-applied asphalt emulsionbefore it is dried.

Impregnated Reinforcing Sheet

In still another approach, the emulsion breaker can be provided byapplying to the substrate a new building product comprising a fibrous orforaminous, preferably flexible, web or layer of material impregnatedwith the emulsion-breaking agent. For example, the emulsion breaker inliquid form can be impregnated into such a web or layer in a factory andthen allowed to dry to produce a building product that can be stored,shipped and then applied to the substrate long after it is made.Alternatively, such a building product can be made on the job site byspraying the web or layer with the emulsion breaker in liquid form, andthen applying the building product so made to the substrate. Or, thefibrous or foraminous web or layer can be applied to the substrate firstand then impregnated with the emulsion breaker second. In any event,when the aqueous asphalt emulsion is then applied to such a buildingproduct, it will immediately break into its aqueous and organic phasesas a result of contact with the emulsion breaker impregnated into thisproduct.

In still another approach, the new building product described above canbe contacted with the aqueous asphalt emulsion after the emulsion isapplied to the substrate, before the emulsion is dried. Once again,contact of the asphalt emulsion with the emulsion breaker in thisbuilding product will cause the emulsion to break into its aqueous andorganic phases, thereby liberating this aqueous phase for easy and rapiddrying.

The emulsion breaker-impregnated reinforcing sheet described above canbe made from any fibrous or foraminous web or layer material which willreceive the aqueous asphalt emulsion among its interstices and whichwill also receive and hold on the surfaces of these interstices asuitable amount of the emulsion breaker. Examples includes webs andlayers made from essentially any naturally-occurring or syntheticmaterial, and specifically include those materials normally used inmaking the base or reinforcing sheets mentioned above in connection withforming conventional asphalt roofing systems. Particular examplesinclude fiberglass and polyester.

Finishing Layers

In still another approach, the technology of this disclosure can be usedto special advantage in producing roofing systems having finishinglayers based on reflective acrylic emulsions. Reflective white roofingsystems based on acrylic emulsions, optionally filled with heat and/orlight reflective fillers, are becoming increasingly popular in warmerclimates. When such finishing layers are applied a top conventionalasphalt roofing systems, it necessary to wait two weeks or longer forthe asphalt roofing system to set and dry before applying the reflectiveacrylic emulsion. Moreover, it is also necessary to limit the amount ofacrylic emulsion applied to 2 gal./sq. (a “square” is 100 square feet)and to wait 24 hours before applying a second layer of the acrylicemulsion. If desired, the delay between the first and second acrylicemulsion layers can be shortened by including a cement curative in theacrylic emulsion.

In accordance with the technology of this disclosure, however, it hasbeen found that the such acrylic emulsion finishing layers can beapplied with little or no delay after application of the asphalt roofingsystem of this disclosure is complete. For example, such decorativeacrylic emulsions can be applied within 24 hours, and even on the sameday as, the last asphalt layer of this asphalt roofing system isapplied. Moreover, acrylic emulsion layers ≧4 gal./sq., ≧6 gal./sq. andeven ≧8 gal./sq can be applied in a single application, since theemulsion-breaker in this asphalt roofing system also initiates cure ofthis material. This greatly reduces costs, not only because long delaysare avoided, but also because labor requirements are substantiallyreduced.

Uses

As indicated above, the technology of this disclosure can be used in anyapplication where aqueous asphalt emulsions have previously been used,or will be used. Nonetheless, this technology finds particularapplicability where fast drying of an aqueous asphalt emulsion is anadvantage.

Moreover, this technology also enables aqueous asphalt emulsions to beused in new applications such as in providing quick set insulationadhesive for instant green strength, as the binder component incast-in-place roof applications, and for repair and patch applicationsto give instant water proofing performance.

EXAMPLES

In order to more thoroughly describe this technology, the followingworking examples are provided:

Comparative Example A

An SBR-modified (Styrene Butadiene Rubber-modified) asphalt emulsioncontaining 62.48 weight solids and having a of pH 10.32 and a density of8.25 lb/gal was prepared by combining the ingredients listed in Table 1:

TABLE 1 Composition of SBR-Modified Asphalt Emulsion Weight IngredientGeneric Composition Commercial Name % Asphalt Asphalt AC-17 50 Tap WaterN/A N/A 27 Emulsifier Soap Vinsol/Caustic Soda .6 Latex SBR Intex 13216.5 Mineral Spirits Aliphatic Hydrocarbon Exxol D40 4.1 Aqua AmmoniaAmmonium Hydroxide Aqua Ammonia .3 Thickener Polyacrylic Acid AcrysolASE-95 1.5

A three-ply built-up roofing system was prepared on a sunny, 62° F., 40%humidity day by applying a layer of the above asphalt emulsion onto theroof foundation at a rate of 4 gal/sq. to provide a coating 64 wet milsthick (A “wet mil”= 1/1000 inch of uncured coating) using a hydraulicpump at 2000 psi with a 0.099 spray tip and a 32-inch fan pattern. Areinforcing layer composed of a stitch-bonded polyester fiber mat scrimwas then applied in shingle fashion, promptly rolled into the emulsionand then broomed to eliminate wrinkles and ensure positive embedment.Two additional scrim/asphalt plies were then applied in the same way.

After two weeks, the asphalt emulsion had completely set up and a firstwhite acrylic coating was applied at rate of 2 gal/sq. When this firstwhite acrylic coating had finally dried, which took approximately 24hours, a second white acrylic coating was applied also at a rate of 2gal/sq. After an additional 24 hours, this second acrylic coating hadcompletely set and completely dried within 2 weeks, thereby producingthe final roofing system of this example.

Example 1

Comparative Example A was repeated except that the stitch-bondedpolyester fiber mat used to form the reinforcing layer was firstimpregnated with 0.5 gal/sq. of a calcium chloride pretreating solutioncontaining the ingredients listed in the following Table 2 and allowedto dry before being used:

TABLE 2 Composition of Calcium Chloride Pre-treating Solution IngredientGeneric Composition Commercial Name Weight % Tap Water N/A N/A 94Breaking Agent Calcium Chloride Calcium Chloride 5 Wetting AgentSilicone Surfactant BYK-156 1

Drying and set up of this 3-ply scrim/asphalt system was completed in 24hours rather than two weeks in the case of Comparative Example A.

As in the case of Comparative Example A, a decorative white acrylicfinishing layer was applied to this asphalt roofing system as well.However in this instance, a single white acrylic layer could be appliedat a rate of 4 gal/sq. rather than two successive white acrylic layersat a rate of 2 gal/sq. per layer, since the CaCl₂ impregnant in thescrim initiated cure of this thicker acrylic layer.

Comparative Example B

An SBR Asphalt Emulsion (Table I) was applied to an asphalt ply sheet ata rate of 3 gal/sq at 25° C. and 50% relative humidity. The SBR AsphaltEmulsion so applied set up and achieved rain-off resistance (35 psi/30minutes) within 2½ hours of application.

Example 2

Comparative Example B was repeated, except that the asphalt ply sheetwas primed with 0.25 gal/sq of the calcium chloride based primerdescribed in Table 3 and allowed to dry before application of theasphalt emulsion.

TABLE 3 Composition of Calcium Chloride Primer Ingredient GenericComposition Commercial Name Weight % Tap Water N/A N/A 89 Breaking AgentCalcium Chloride Calcium Chloride 10 Wetting Agent Silicone SurfactantBYK-156 1

The SBR Asphalt Emulsion achieved set up and rain-off resistance (35psi/30 minutes) in 5 minutes after application, which is much fasterthan the 2½ hours required in Comparative Example B.

Example 3

A three-ply built-up roofing system was prepared in general accordancewith Comparative Example A and Example 1, with only a portion of thisroofing system being made with the calcium chloride-impregnated scrim ofthis invention. The system set up overnight and then a white acryliccoating was applied to the top scrim. Within 15 minutes a thunderstormpassed through with a significant amount of rain. The white acryliccoating completely washed off the roofing system, except where thetreated scrim was located.

Although only a few embodiments have been described in this disclosure,many modifications can be made without departing from the spirit andscope of the technology disclosed here. All such modifications areintended to be included within the scope of this technology, which is tobe limited only by the following claims.

The invention claimed is:
 1. A process for shortening the time neededfor an aqueous asphalt emulsion to dry after the emulsion has beenapplied to a substrate by a single component sprayer, the process beingcarried out without simultaneous application to the substrate of anemulsion breaker along with the asphalt emulsion, the process comprisingcontacting the emulsion with a reinforcing sheet comprising a fibrous orforaminous web or layer of material impregnated with a dried emulsionbreaker.
 2. The process of claim 1, wherein the aqueous asphalt emulsionis applied to the substrate and thereafter the reinforcing sheet isapplied to the aqueous asphalt emulsion.
 3. The process of claim 1,wherein the reinforcing sheet is applied to the substrate and thereafterthe aqueous asphalt emulsion is applied to the reinforcing sheet.
 4. Theprocess of claim 1, wherein the aqueous asphalt emulsion includes ananionic emulsifier and further wherein the emulsion breaker is selectedfrom the group consisting of calcium chloride, calcium nitrate, aluminumchloride and ferric chloride.
 5. The process of claim 1, furthercomprising applying a reflective acrylic emulsion layer to thewaterproofing asphalt layer.
 6. The process of claim 5, wherein thereflective acrylic emulsion layer is applied to the waterproofingasphalt layer within 24 hours of the application of the waterproofingasphalt layer to the substrate.
 7. The process of claim 6, wherein theacrylic emulsion layer is applied in an amount of ≧4 gal./sq.
 8. Theprocess of claim 5, wherein the reflective acrylic emulsion layer isapplied to a reinforcing sheet comprising a fibrous or foraminous web orlayer of material impregnated with the emulsion breaker.
 9. A processfor shortening the time needed for an apueous asphalt emulsion to dryafter the emulsion has been applied to a substrate comprising contactingthe emulsion with a reinforcing sheet comprising a fibrous or foraminousweb or layer of material impregnated with a dried emulsion breaker.